In 1996, Plato became a councillor and full-time politician. He served two terms as Chairperson of the City of Cape Town's Economic Development, Tourism and Property Management Portfolio Committee and, from 2006 to 2009, held the Housing Portfolio in the Mayoral Committee. During this period, as Deputy Chairperson of the DA Metro Region and DA Caucus in the City of Cape Town, he also served as Acting Executive Mayor at various intervals. Shortly before being elected Executive Mayor in May 2009, Plato had taken over as the Mayoral Committee Member responsible for Service Delivery and Economic Development.

As a dedicated ward councillor serving Belhar, Uitsig and Ravenmead, Plato was and continues to be committed to social upliftment and poverty alleviation. During his term as mayor, he introduced many job creation projects and made this one of the focus points of his mayoral agenda.